title: Synergistic interaction and mode of action of Citrus hystrix essential oil against bacteria causing periodontal diseases.
abstract: BACKGROUND
  Citrus hystrix de Candolle (Rutaceae), an edible plant regularly used as a food ingredient, possesses antibacterial activity, but there is no current data on the activity against bacteria causing periodontal diseases.
  
  
  OBJECTIVE
  C. hystrix essential oil from leaves and peel were investigated for antibiofilm formation and mode of action against bacteria causing periodontal diseases.
  
  
  METHODS
  In vitro antibacterial and antibiofilm formation activities were determined by broth microdilution and time kill assay. Mode of action of essential oil was observed by SEM and the active component was identified by bioautography and GC/MS.
  
  
  CONCLUSIONS
  C. hystrix leaves oil exhibited antibacterial activity at the MICs of 1.06 mg/mL for P. gingivalis and S. mutans and 2.12 mg/mL for S. sanguinis. Leaf oil at 4.25 mg/mL showed antibiofilm formation activity with 99% inhibition. The lethal effects on P. gingivalis were observed within 2 and 4 h after treated with 4 × MIC and 2 × MIC, respectively. S. sanguinis and S. mutans were completely killed within 4 and 8 h after exposed to 4 × MIC and 2 × MIC of oil. MICs of tested strains showed 4 times reduction suggesting synergistic interaction of oil and chlorhexidine. Bacterial outer membrane was disrupted after treatment with leaves oil. Additionally, citronellal was identified as the major active compound of C. hystrix oil.
  
  
  CONCLUSIONS
  C. hystrix leaf oil could be used as a natural active compound or in combination with chlorhexidine in mouthwash preparations to prevent the growth of bacteria associated with periodontal diseases and biofilm formation.
authors.affiliation: Department of Microbiology .
authors.forename: Karn
authors.initials: K
authors.lastname: Wongsariya
authors.forename: Phanida
authors.initials: P
authors.lastname: Phanthong
authors.forename: Nuntavan
authors.initials: N
authors.lastname: Bunyapraphatsara
authors.forename: Vimol
authors.initials: V
authors.lastname: Srisukh
authors.forename: Mullika Traidej
authors.initials: MT
authors.lastname: Chomnawang
mesh_terms: D000080462:Acyclic Monoterpenes; D000447:Aldehydes / Q000302:isolation & purification; D000900:Anti-Bacterial Agents / Q000008:administration & dosage / Q000302:isolation & purification / Q000494:pharmacology*; D001419:Bacteria / Q000187:drug effects; D018441:Biofilms / Q000187:drug effects; D002710:Chlorhexidine / Q000008:administration & dosage / Q000494:pharmacology; D002957:Citrus / Q000737:chemistry*; D004357:Drug Synergism; D008401:Gas Chromatography-Mass Spectrometry; D008826:Microbial Sensitivity Tests; D008855:Microscopy, Electron, Scanning; D039821:Monoterpenes / Q000302:isolation & purification; D009822:Oils, Volatile / Q000008:administration & dosage / Q000302:isolation & purification / Q000494:pharmacology*; D010510:Periodontal Diseases / Q000382:microbiology; D010936:Plant Extracts / Q000008:administration & dosage / Q000494:pharmacology*; D018515:Plant Leaves; D013997:Time Factors
chemical_list: D000080462:Acyclic Monoterpenes; D000447:Aldehydes; D000900:Anti-Bacterial Agents; D039821:Monoterpenes; D009822:Oils, Volatile; D010936:Plant Extracts; C108217:citronellal; D002710:Chlorhexidine